A difficult obstacle associated with the exploration and production of oil and gas is management of significant ocean currents. These currents can produce vortex-induced vibration (VIV) and/or large deflections of tubulars associated with drilling and production. VIV can cause substantial fatigue damage to the tubular or cause suspension of drilling due to increased deflections.
Two solutions for VIV suppression are helical strakes and fairings. Typically, helical strakes are made by installing fins helically around a cylindrical shell. The cylindrical shell may be separated into two halves and positioned around the tubular to helically arrange the fins around the underlying tubular. While helical strakes, if properly designed, can reduce the VIV fatigue damage rate of a tubular in an ocean current, they typically produce an increase in the drag on the tubular and hence an increase in deflection. Thus, helical strakes can be effective for solving the vibration problem at the expense of worsening the drag and deflection problem.
Another solution is to use fairings as the VIV suppression device. Typical fairings have a substantially triangular shape and work by streamlining the current flow past the tubular. A properly designed fairing can reduce both the VIV and the drag. Fairings can be made to be free to weathervane around the tubular in response to changes in the ocean current.
Fairings and helical stakes have been used to suppress VIV for many applications in the past. They have also been retrofit to tubulars; that is they have been installed underwater after the tubular is in place.
A difficulty with most retrofit suppression designs, however, is that they require tooling to interface with a remote operated vehicle (ROV) for installation. This tooling can be substantial. The tooling can be expensive, difficult and unsafe to use, and requires a slow process for installation of the suppression devices. In addition, it can take months, or even years, to design and fabricate tooling for ROV installation of VIV suppression devices.